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There is described an inspection system (10) for inspecting the quality of printed sheets which are transported by a sheet conveyor system comprising at least one sheet gripper system (3a, 3b) including a plurality of spaced-apart gripper bars (32) for holding the printed sheets by a leading edge th

There is described an inspection system (10) for inspecting the quality of printed sheets which are transported by a sheet conveyor system comprising at least one sheet gripper system (3a, 3b) including a plurality of spaced-apart gripper bars (32) for holding the printed sheets by a leading edge thereof. The inspection system (10) comprises an optical quality control apparatus for carrying out inspection of a first side of the printed sheets while the printed sheets are being transported by the sheet gripper system (3b). The optical quality control apparatus includes a line camera (11) for scanning the first side of the printed sheets at an inspection location which is situated at a location proximate to a portion of the sheet gripper system (3b) where the gripper bars (32) transporting the printed sheets undergo a change of direction of displacement while the printed sheets are still being scanned by the line camera (11). The inspection system (10) further comprises a suction roller (50) that is placed in front of the optical path (B) of the line camera (11) along the path (A) of the printed sheets being transported by the sheet gripper system (3b), which suction roller (50) contacts a second side of the printed sheets opposite to the first side which is being scanned by the line camera (11), the suction roller (50) being driven at a selected circumferential speed to drive successive portions of the printed sheets being inspected by the quality control apparatus at a determined and controlled speed past the line camera (11).

대표청구항 ▼

1. An inspection system for inspecting the quality of printed sheets which are transported by a sheet conveyor system comprising at least one sheet gripper system including a plurality of spaced-apart gripper bars for holding the printed sheets by a leading edge thereof, said inspection system compr

1. An inspection system for inspecting the quality of printed sheets which are transported by a sheet conveyor system comprising at least one sheet gripper system including a plurality of spaced-apart gripper bars for holding the printed sheets by a leading edge thereof, said inspection system comprising an optical quality control apparatus for carrying out inspection of a first side of the printed sheets while the printed sheets are being transported by the sheet gripper system, wherein said optical quality control apparatus includes a line camera for scanning the first side of the printed sheets at an inspection location which is situated at a location proximate to a portion of the sheet gripper system where the gripper bars transporting the printed sheets undergo a change of direction of displacement while the printed sheets are still being scanned by the line camera,said inspection system further comprising a suction roller that is placed in front of the optical path of the line camera along the path of the printed sheets being transported by the sheet gripper system, which suction roller contacts a second side of the printed sheets opposite to the first side which is being scanned by the line camera, said suction roller being driven at a selected circumferential speed to drive successive portions of the printed sheets being inspected by the optical quality control apparatus at a determined and controlled speed past the line camera,wherein said suction roller comprises a plurality of aspiration openings and an adjustment mechanism configured to selectively close part of the plurality of aspiration openings in dependence of the width of the printed sheets to be inspected,wherein said adjustment mechanism comprises a rotatable adjustment member provided with a plurality of rows of apertures of varying numbers extending transversally to the direction of displacement of the sheets. 2. An inspection system for inspecting the quality of printed sheets which are transported by a sheet conveyor system comprising at least one sheet gripper system including a plurality of spaced-apart gripper bars for holding the printed sheets by a leading edge thereof, said inspection system comprising an optical quality control apparatus for carrying out inspection of a first side of the printed sheets while the printed sheets are being transported by the sheet gripper system, wherein said optical quality control apparatus includes a line camera for scanning the first side of the printed sheets,said inspection system further comprising:a suction roller that is placed in front of the optical path of the line camera along the path of the printed sheets being transported by the sheet gripper system, which suction roller contacts a second side of the printed sheets opposite to the first side which is being scanned by the line camera; anda suction box located immediately before said suction roller with respect to a direction of displacement of the printed sheets and cooperating with said second side of the printed sheets for aspirating at least a portion of the second side of the printed sheets against a substantially flat surface of the suction box before contacting the suction roller,wherein said suction roller comprises a plurality of aspiration openings and an adjustment mechanism configured to selectively close part of the plurality of aspiration openings in dependence of the width of the printed sheets to be inspected,wherein said adjustment mechanism comprises a rotatable adjustment member provided with a plurality of rows of apertures of varying numbers extending transversally to the direction of displacement of the sheets. 3. The inspection system as defined in claim 2, wherein said suction roller is driven at a selected circumferential speed to drive successive portions of the printed sheets being inspected by the optical quality control apparatus at a determined and controlled speed past the line camera. 4. The inspection system as defined in claim 1, wherein rotation of the suction roller is synchronized with the displacement of the gripper bars. 5. The inspection system as defined in claim 4, wherein a circumference of said suction roller is a fraction of the distance between two successive gripper bars. 6. The inspection system as defined in claim 4, further comprising chains driving the gripper bars and a mechanical coupling provided between the suction roller and the chains, wherein the suction roller is driven into rotation by chains driving the gripper bars through the mechanical coupling. 7. The inspection system as defined in claim 1, wherein said suction roller is driven by a separate drive. 8. The inspection system as defined in claim 1, further comprising a single-turn shaft which is driven into rotation by chains driving the gripper bars in such a way as to perform one complete revolution corresponding to the frequency of passage of successive gripper bars. 9. The inspection system as defined in claim 8, wherein a shaft encoder is provided on said single-turn shaft, which shaft encoder is used to synchronise operation of the optical quality control apparatus with the passage of the printed sheets. 10. The inspection system as defined in claim 1, wherein the sheet gripper system comprises lower and upper gripper paths along which the gripper bars are led, the printed sheets being transported by the sheet gripper system on said lower gripper path with said first side oriented upwards, and wherein said line camera is located above said lower gripper path and looks towards the first side of the printed sheets being transported on said lower gripper path. 11. A printing press comprising: a printing unit for printing sheets;a delivery unit;a sheet conveyor system for transporting the printed sheets from the printing unit to the delivery unit, which sheet conveyor system comprises at least one sheet gripper system including a plurality of spaced-apart gripper bars for holding the printed sheets by a leading edge thereof; andan inspection system according to claim 1 placed along the path of said sheet gripper system. 12. The inspection system as defined in claim 2, wherein rotation of the suction roller is synchronized with the displacement of the gripper bars. 13. The inspection system as defined in claim 12, wherein a circumference of said suction roller is a fraction of the distance between two successive gripper bars. 14. The inspection system as defined in claim 12, further comprising chains driving the gripper bars and a mechanical coupling provided between the suction roller and the chains, wherein the suction roller is driven into rotation through the mechanical coupling. 15. The inspection system as defined in claim 2, wherein said suction roller is driven by a separate drive. 16. The inspection system as defined in claim 2, further comprising a single-turn shaft which is driven into rotation by chains driving the gripper bars in such a way as to perform one complete revolution corresponding to the frequency of passage of successive gripper bars. 17. The inspection system as defined in claim 16, wherein a shaft encoder is provided on said single-turn shaft, which shaft encoder is used to synchronise operation of the optical quality control apparatus with the passage of the printed sheets. 18. The inspection system as defined in claim 2, wherein the sheet gripper system comprises lower and upper gripper paths along which the gripper bars are led, the printed sheets being transported by the sheet gripper system on said lower gripper path with said first side oriented upwards, and wherein said line camera is located above said lower gripper path and looks towards the first side of the printed sheets being transported on said lower gripper path. 19. A printing press comprising: a printing unit for printing sheets;a delivery unit;a sheet conveyor system for transporting the printed sheets from the printing unit to the delivery unit, which sheet conveyor system comprises at least one sheet gripper system including a plurality of spaced-apart gripper bars for holding the printed sheets by a leading edge thereof; andan inspection system according to claim 2 placed along the path of said sheet gripper system. 20. The inspection system as defined in claim 1, further comprising a suction box located immediately before said suction roller with respect to the direction of displacement of the printed sheets and cooperating with said second side of the printed sheets for aspirating at least a portion of the second side of the printed sheets against a substantially flat surface of the suction box before contacting the suction roller.